"A number of states, including my home state of Maine, have now legalized same-sex marriage, and I agree with that decision," she said in a release on Wednesday.

"Today, same-sex couples can be legally married in 19 states and the District of Columbia. Nearly 44 percent of Americans live in a state where same-sex couples can be legally married, and I believe this number will only continue to grow," she said.

Collins' announcement occurred on the same day she was endorsed by the Human Rights Campaign, which praised Collins for her support of lesbian, gay, bisexual and transgender equality through her support of ending "Don't ask, don't tell" in the U.S. armed forces. The policy allowed LGBT people to continue to serve, but were not to disclose anything related tosexual orientation.

Collins' opponent, Shenna Bellows, had criticized Collins earlier in the day on Wednesday for lack of support of same-sex marriage.

"Remaining silent on some of the biggest civil rights issues of our generation, even after the voters have spoken, isn't leadership, and it isn't how Maine became one of the most inclusive states in the country for LGBT rights," Bellows said in a statement.

Bellows noted that when she was head of the American Civil Liberties Union in Maine, she helped to lead the fight in support of a referendum in favor of same-sex marriage in 2012. The referendum passed, which allowed gay and lesbian couples to marry in Maine.

Hillary Clinton did not have a State Department email account while she served as America's top diplomat, a senior state department official said Monday, and instead used a personal email account during her four years on the job.